I finally got around to actually changing the batteries in my SARLINK PLB. Took about an hour and 15 minutes.

Open back of unit. Disconnect and remove two battery stacks.

Unsolder 2 solder connections on each of the two battery packs.
Solder two new batteries nose to tail. Repeat for 2nd pair.
Solder 4 wire connectors to battery tabs.
Tape/insulate appropriately.
Install.
Self test both beacon and GPS - PASS BOTH.

Label unit with next battery change date 3/2023.